Near- and mid- infrared group IV photonics · Silicon Photonics: Market Predictions . ... School of EEE-NTU 10 Silicon Photonics: Applications in Quantum Photonics •Silicon photonics

Si Technologies Centre of Excellence

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Near- and mid- infrared group IV photonics

C. G. Littlejohns1,2, M. Saïd Rouifed1, H. Qiu1, T. Guo Xin1, T. Hu1, T. Dominguez Bucio2, M. Nedeljkovic2, G. Z. Mashanovich2, G. T. Reed2, F. Y.

Gardes2, H. Wang1

1Novitas, Nanoelectronics Centre of Excellence, Nanyang Technological University, 50 Nanyang Avenue, Singapore,

639798. 2Optoelectronics Research Centre, Building 53, University of Southampton, Southampton, SO17 1BJ, UK.

Energy Material and Nanotechnology Meeting on Quantum, Phuket, April 2016.


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Outline

1. Introduction to silicon photonics.

2. Silicon-Germanium-on-Insulator (SGOI) formed by rapid melt growth (RMG).

3. Prospects for mid-infrared silicon photonics.

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Outline




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• 1 Zetabyte of internet traffic per year this year • Doubled by 2019

Source: Cisco Visual networking Index Global Forecast, 2014-2019.

1 zetabyte = 1012 gigabytes 1 exabyte = 109 gigabytes

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Silicon Photonics: Internet Traffic Predictions

Expanding bandwidth requirements: • Content delivery:

Digital game purchases. Live streaming. Increasing video resolution

standards (HDTV, UHDTV…).

• Cloud computing: Microsoft Azure. Amazon EC2. Chrome OS.

Source: Intel website, 2014.

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• In 2010, Google disclosed a typical global power consumption of ~ 260 Megawatts of power1.

• Google’s data centres account for less than 1% of the power used by data centres in 20102.

• In 2010, data centres are thought to have accounted for ~1.5% of the global power consumption.

• If we double bandwidth without increasing power efficiency, we need more power plants!

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Source: 1New York Times - Google Details, and Defends, Its Use of Electricity. 2Jonathon Koomey - Growth in data center electricity use 2005 to 2010.

Silicon Photonics: What about Power?

Images: Google


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• Optics should ideally use less power than current wire interconnects:

<1 pJ/bit for off-chip1,2.

<50-220 fJ/bit for global on-chip1,2.

• CMOS compatibility:

Control costs by utilising existing CMOS infrastructure and processes.

• Components:

Light source. Waveguides. Wavelength Division Multiplexers (WDM). Modulators. Detectors. Switches and Routers.

• Dense spatial connections & WDM (section 2).

Source: 1D. A. B. Miller, Proc. IEEE 97, 1166 - 1185 (2009). 2G T Reed et al, Nature Photonics 8, 518 – 526, (2010). 7

Silicon Photonics: Requirements for Optical Interconnects

Image: Intel.


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• The prospect of integrating CMOS electronics and photonics on the same substrate:

Greater functionality.

Improved performance.

Cost reductions.

• Mature processing derived from years of

development in the electronics industry.

• High refractive index contrast (compact components).

• Lower power interconnects.

• Massive interconnect density (WDM).

• Low cost for mass markets.

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Silicon Photonics: Why is Silicon Photonics the Answer?

Image: Intel.


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9 Source: Silicon Photonics Report - Yole Développement.

Silicon Photonics: Market Predictions


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Silicon Photonics: Applications in Quantum Photonics • Silicon photonics promises a fully integrated system platform for a range of quantum applications:

Quantum Communications.

Quantum sensing.

Quantum computation and simulation.

• Devices already demonstrated.

Single Photon Source Single Photon Avalanche Detector

Davanco et al., Applied Physics Letters, 2012.

Warburton et al, IEEE Transactions on Electronic Devices, 2013.


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Crystalline SiGe-on-Insulator: Motivation

1. Tuneable bandgap (modulators etc.).

2. Tuneable lattice constant (epitaxial growth etc.).

3. Higher carrier mobilities than Si (BiCMOS drivers etc.).

4. Ability to fabricate low power electro-absorption (EA) modulators.

Dismukes, J. et. al, Lattice parameter and density in germanium-silicon alloys. J. Phys. Chem. 68, 3021-3027 (1964).

Braunstein, R. et. al, Intrinsic optical absorption in germanium-silicon alloys. Phys. Rev. 109, 695-710 (1958).

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Crystalline SiGe-on-Insulator: RMG Fabrication Process

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Crystalline SiGe-on-Insulator: RMG Growth Mechanism

• Si diffuses from seed into Ge strip whilst in liquid phase forming SiGe. • Growth initiates at the Si seed area. • Epitaxial growth front propagates along SiGe strip. • Defects confined to seed area.

SiO2

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Crystalline SiGe-on-Insulator: RMG Layer Characterisation

SiGe phase diagram SiGe composition along straight strips

Olesinski, R. W. et al. Bulletin of Alloy Phase Diagrams 5,

180-183 (1984).

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Crystalline SiGe-on-Insulator: Composition Profile Engineering • Must increase regrowth front propagation speed:

Therefore, must increase the cooling rate.

SEM

• Branches, or ‘radiating elements’, increase the cooling rate of the central strip

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Crystalline SiGe-on-Insulator: Uniform Composition • Uniform composition profile is achieved by narrowing the central strip to 3 µm:

Branches provide sufficient cooling for steady-state solidification to occur.

C. G. Littlejohns et al, “Next generation device grade silicon-germanium on insulator,” Scientific Reports, vol. 5, 8288, 2015. 17


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• Higher anneal temperature means that solidification does not begin until more Si has diffused into the SiGe layer.

Crystalline SiGe-on-Insulator: Composition Tuning by Anneal Temperature

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Crystalline SiGe-on-Insulator: Composition Tuning by Structural Design

• Combine straight strip properties with tree-structure properties.

• Enables, multiple uniform composition SiGe compositions to be simultaneously formed.

• Only requires one initial deposition step and one anneal step.

C. G. Littlejohns et al., “Towards a fully functional integrated photonic-electronic platform via a single SiGe growth step”, Scientific Reports, vol. 5, 19425, 2016. 19


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Crystalline SiGe-on-Insulator: Quantum Based Applications

Chaisakul et al., Nature Photonics, 2014.

SiGe quantum well based optical interconnects.

Liu et al., Nature Photonics, 2011.

Seed layer for InGaAs quantum dot lasers.

Rapid melt growth removes the need for thick (8 µm) SiGe buffer layers meaning integration with SOI is much simpler.


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Outline




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Mid-IR Silicon Photonics: Motivation

Homeland security

Laser detection of explosive devices, or dangerous substances. Most of explosive chemicals show specific absorption footprints in mid-IR region.

Telecomms/datacomms

Optical fiber communication

Healthcare

Lab on a chip: Infrared spectroscopy aids decease diagnosis Mid-IR Photonics

Environmental Monitoring

CO2, N2O, CO, butane & methane etc. have strong absorptions in mid-IR

(2 to 5 µm) region.

http://3.bp.blogspot.com/-7Zm-IrWIbTo/T5rNrmDXnqI/AAAAAAAAB8Y/_v-IcTwtDlo/s1600/Russian_invisible_laser_bomb_detector_makes_molecular_scan-at_50_meters_001.jpg


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Dimensions Size (μm)

WMMI 6

LMMI 26

Win 1.3

S 1.7

D 3 23

Mid-IR Silicon Photonics: Passive Devices

Simulated MMI transmission.

• Example device - multimode interferometer (MMI): Design optimised using Lumerical Mode Solutions. λ = 2 µm, 400 nm Si / 2 µm BOX SOI wafer. Written by e-beam lithography (EBL). Etched by reactive ion etching (RIE):

Slab height = 100 nm.


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• Data normalised using a straight waveguide. • The propagation losses for a rib waveguide are

around 3~4 dB/cm. • MMI’s are cascaded to calculate insertion loss:

Insertion loss: 0.9 ± 0.1 dB/MMI. Measured MMI length is 25.2 µm:

Device optimised for 26 µm length.

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Mid-IR Silicon Photonics: Passive Device Measurements

Loss = 0.9±0.1dB/MMI

Measured transmission through cascaded MMI’s.

Fabricated MMI.

Waveguide cross-section.


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Conclusions

• Silicon photonics promises to play a significant role in future technology:

For this to become a reality mass production is necessary.

• Rapid melt growth of SGOI enables multiple compositions to be simultaneously grown:

High quality material is suitable for state-of-the-art devices, at a low cost.

• Mid-IR silicon photonics could lead new technologies in sensing:

Ge-on-Si platform promises more efficient active devices for mid-IR wavelengths.

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HERMES High dEnsity Silicon

GeRManium intEgrated photonicS

Acknowledgements

Email: [email protected]

This work is supported by National Research Foundation of Singapore (NRF-CRP12-2013-04). Image: NTU Learning Hub

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Near- and mid- infrared group IV photonics · Silicon Photonics: Market Predictions . ... School of EEE-NTU 10 Silicon Photonics: Applications in Quantum Photonics •Silicon photonics